Ciliary epithelium is the site producing aqueous humor. In this study, we investigated the calcium second messenger system in the ciliary nonpigment epithelial cells. Dutch rabbit were used for the experiments. Ciliary body was extracted from the eye and ciliary nonpigmented epithelial layer was isolated by incubating the tissue in low calcium medium for a short period. Cells were incubated at 37℃ for 50 minutes in solution containing 5 μM fura-2/AM. The concentration of the intracellular free calcium ion ([CaィイD12+ィエD1]ィイD2iィエD2) was observed with an ARGUS-20/CA system (Hamamatsu photonics) and an inverted microscope (TE300, Nikon). Ten μM clonidine, 100 μM acetylcholine, 10 μM phenylephrine, and 1 μM epinephrine induced the increase of [CaィイD12+ィエD1]ィイD2iィエD2. One hundred μM isoproterenol caused no increase of [CaィイD12+ィエD1]ィイD2iィエD2. Addition of 100 μM clonidine after the application of 1 μM acetylcholine induced strong increase of [CaィイD12+ィエD1]ィイD2iィエD2. Addition of 100 μM isoproterenol after the 10 μM phenylephrine caused no intracellular calcium ion response. The application of 1 mM octanol before the stimulation by 10 μM phenylephirine did not change the response of the cells. Thus, it was proved that there was an interaction between the intracelluar calcium ion mobilization by muscarinic agonists and alpha2-adrenergic agonists while the interaction between alpha1-adrenergic agonists and beta-adrenergic agonists could not be observed and it is suggested that the gap junction may not play a major role in signal transduction of calcium ion second messenger system.